The purpose of a forum is to exchange ideas, but people prefer to use them to feed their egos, hence they are either aggressively attacking someone else to appear stronger than they are, or they are defending themselves against these attacks. Someone who wishes to use a forum properly neither attacks others personally or bothers to defend themselves against personal attacks, this does not mean that one does not attack or defend ideas. Also most forum users confuse the two, if you attack their ideas they believe you are insulting them, if you defend your ideas they believe you are being egotistical.